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L30ALM signal
Asking about L30ALM signal in MKV and how it is generated
By BALI abdelaziz on 13 January, 2009 - 3:09 am

Hello, good year and peace upon you,

I noticed:
- The buzzer of TCTG is activated when the L30ALM signal is true.
- For each Process or diagnostic alarm the L30ALM signal becomes true.
- It will be false only when we force it to Zero, or when we press on the silence and Ack button in Cimlicity HMI.

Firstly, I want to understand exactly how the L30ALM signal is generated. No trace in CSP. Secondly, what is the link between L30ALM signal and a Silence or Ack button in alarm screen of Cimplicity HMI?

Thanks in advance.

1 out of 1 members thought this post was helpful...

The function of L30ALM is to provide a logic signal that is set to a logic "1" whenever a Process- or Diagnostic Alarm is annunciated. That is done in "firmware".

The real purpose of the signal is to allow it to be used to drive a relay (discrete) output which can be used to switch the power to some kind of alarm indicator, either audible or visual (flashing light, etc.).

L30ALM will be returned to a logic "0" when the operator silences the alarm. Alarm Management, as I was taught by GE instructors, involves the act of, 1) Silencing the audible alarm horn when it has attracted my attention and directed me to look at the Alarm Window or Alarm Display; 2) reading the alarm text which is attempting to indicate what alarm condition has been detected and then Acknowledging the alarm (the indication that the operator has read and *understood* the alarm condition); 3) Resolving the alarm condition (in other words, take some kind of corrective action to investigate and "eliminate" the alarm condition); and last, 4) Resetting the alarm from the Alarm Display and Alarm Window.

So, any time any alarm is detected and annunciated (displayed in the Alarm Window and Alarm Display) L30ALM is set to a logic "1". (At the same time, the internal audible alarm horn/buzzer will also be energized.) L30ALM can be dropped out (set back to a logic "0") by Silencing all active alarms in the Alarm Window and Alarm Display. (When all active alarms have been silenced, the internal audible alarm horn/buzzer will be de-energized.)

In this way, it mimics the operation of the internal Speedtronic turbine control system logic that drives the internal audible alarm horn/buzzer of the Mark IV and Mark V (most Mark VIs and Mark VIes don't have internal audible alarm buzzers; probably a cost-reduction move). Since it mimics the operation of the logic that drives the panel audible alarm buzzer, it can also drive an external alarm indicator in the same fashion, using the Alarm Silence button to stop the external alarm horn or visual alarm indicator.

This signal can also be used via MODBUS or GSM to drive remote alarm indications via the remote control system that is monitoring the MODBUS or GSM link.

By Chiranjeevi on 3 July, 2017 - 11:10 am


This L30ALM given for driving an O/P which is on 1E4A, TDBT card relay 07 and it is r30horn. but i did not check whether it is giving potential free or a wet contact.

Can you explain?

1 out of 1 members thought this post was helpful...


I don't have access to any Speedtronic manuals or drawings at the writing, but if I recall correctly--from the PDOA section of GEH-6721, Vol. II, there are drawings of the discreet output circuits of the TDBT, and the first six of the twelve DOs (1-6) can be wet or dry (potential-free), and the next five (7-11), can only be dry, and the last DO (12), can be wet or dry IF there is a separate power source connected to the TDBT. (This twelfth DO is usually used as a wet DO only for ignitors ("spark plugs).)

So, if I recall correctly, DO 7 on a TDBT is only a dry (potential-free) output--and the voltage source must be supplied from outside the Mark VIe.

If the panel is a Mark VI, the manual is GEH-6421, and the section is VCRC.

In a typical gas turbine Mark VI/VIe panel, the DOs capable of providing voltage (and current), with the exception of #12, are only capable of providing 125 VDC, or maybe 24 VDC if the panel's main power source is 24 VDC.

Hope this helps.

1 out of 1 members thought this post was helpful...


In MarkV or MarkVe or older systems, primary annunciation of any alarm was a horn integrated into one of the control boards itself. But in case of MarkVI and MarkVIe control systems since a Windows based HMI are used, primary alarm annunciation for the HMI will be from the sound output of the HMI PC itself. These sounds are managed by WorkStationST alarm manager in case of MarkVIe systems.

Whenever there is a need in specific projects to activate any external Horns/Annunciation for any alarm from the control system (Process or Diagnostics), L30ALM signal is used.This signal will be driven by an intrinsic variable(from controller firmware) which is set TRUE whenever an alarm condition is present.It is reset whenever the alarm conditions are acknowledged or silenced from HMI. This L30ALM signal will be connected to a DO channel to drive any external Horn/Annunciation.

As explained by CSA, Relay07 channel of any TDBT board in MarkVIe will be a potential free output. So the power for driving the horn in your case must be provided externally.